what do i do after i download a codec to make my movie play?

grrr i am computer retarded and am lost completely. i downloaded a codec from some guys personal website called slave trainer or something, which is under the links page. it was quite odd but yeah I have it. I want to watch my movie but dont know what to do....

i once installed DivX player,just double click the soft ,and choose some settings as the installation is processed ,and then you can watch your moive on it~~i think this soft should be similarly applied